Positron emission tomography (PET) is a medical imaging technique that is commonly used to produce three-dimensional images in vivo. This technique detects gamma rays emitted by a positron-emitting radionuclide tracer that has been administered to a subject. Three-dimensional images of tracer concentrations within the subject's body can then be constructed by computer analysis. In this way, PET can be used, for example, to observe a variety of organs and/or physiological processes such as cellular metabolism and protein synthesis, as well as well as pathological conditions such as cancer and heart disease.
18F-Fluoro-2-Deoxy-D-glucose (18F-FDG) is a common clinical PET probe that is used, for example, to diagnose certain pathological conditions including cancer as well as to evaluate the effects of certain therapeutic regimens. 18F-FDG however, has high absorption ratios in certain tissues such as the brain, heart, kidney and bladder. For this reason, background signals can be a problem when using this molecule at a probe. In addition, some tissues of primary liver cancer and clear cell renal cell carcinoma (CCRCC) do not selectively absorb 18F-FDG, a phenomena that can lead to false negatives. 18F-FDG also has high absorption ratios in inflamed areas, another characteristic which can contribute to erroneous diagnoses. These characteristics of 18F-FDG's limit its applications in vivo.
Compounds useful as probes in positron emission tomography can contain [18F]-2-fluoro-2-deoxyarabinose ([18F]-FDA) as part of the molecule, such as 1-(2′-deoxy-2′-[18F]fluoro-β-D-arabinofuranosyl)cytosine (see, e.g. Radu et al. Nat Med. 2008 July; 14(7):783-8), 1-(2′-deoxy-2′-[18F]fluoro-β-D-arabinofuranosyl)-5-methylcytosine (see, e.g. Shu C J, et. al. J Nucl Med. 2010 July; 51(7):1092-8), and 2′-deoxy-2′-[18F]fluoro-9-β-D-arabinofuranosylguanine (see, e.g. Namavari M, et al. Mol Imaging Biol. 2011 October; 13(5):812-8). However, it has not been determined if any discrete [18F]-FDA compound alone possesses a pharmacokinetic profile that allows it to be used as a PET probe in vivo, much less if a [18F]-FDA compound may be useful to monitor specific physiological processes in vivo.